Medium voltage switchgear assemblies may be provided for rated voltages between 1 kV and 72 kV. High voltage switchgear assemblies may be provided for rated voltages above 72 kV. Switchgear assemblies are utilized in order to distribute an energy flow and to ensure a safe operation within a power net. In order to control the energy flow a switchgear assembly may provide several functions, such as disconnecting, closing and grounding.
Switchgear assemblies may be categorized in gas insulated devices and air insulated devices. In general, air insulated devices may need more space when installed compared to gas insulated devices, since the gas, such as sulfur hexafluoride (SF6) or others, provides improved insulating characteristics compared to air. These differences may influence the dimensions of the switchgear assembly and therefore gas insulated switchgear assemblies may provide a more compact design.
At nominal currents above 1250 A ohmic losses in gas insulated switchgear assemblies are reaching a level, where special measures have to be taken for supporting the heat transfer. These are for example the use of heat sinks inside the gas compartment, conductors with higher cross section and/or painted conductors.
At higher levels, depending very much on the general design of the switchgear assembly, this is no longer sufficient for the heat transfer, because the heat has to pass the housing of the encapsulations. The surface of the housing is defined by the encapsulated volume and in most designs made of plain sheet metal.
According to the common knowledge of a skilled person a gas cooler for a medium voltage switchgear assembly has plain cooling areas with internal and external ribs, mainly made of aluminum. Normally the gas cooler consists of an additional hollow compartment, which is open to one side, with internal and external ribs, being connected to a switchgear gas compartment. The ribs are either part of the housing or connected to the housing as a separate part.
The document EP 1 496 534 B1 discloses a high-power switch with at least one switch pole for guiding and switching an electric current which flows in one current flow direction when the switch is in the closed state. The at least one switch pole contains along a longitudinal axis an inner conductor which carries the current and an outer conductor which is connected to earth potential and carries a return current in the opposite direction to the current. The outer conductor is in the form of a housing, which surrounds the inner conductor. A cooling rib arrangement which contains cooling ribs is provided on the outer conductor and is arranged at a radial distance from the inner conductor.
Furthermore, the document EP 2 157 590 B1 relates to an encapsulated high-voltage switch, containing a heat-generating current conductor, a metal encapsulation surrounding the current conductor, and a cooling element with a cooler. The cooling element is fixed on a part of the encapsulation that is embodied as a mounting plate. Furthermore the cooling element has cooling ribs arranged outside the encapsulation. In a section of the cooler that is embodied as a cooling block, at least a portion of the cooling ribs is arranged parallel to the mounting plate and is held on a heat distributor fixed to the mounting plate and embodied as a plate in such a way that on both sides of the heat distributor in each case one of two groups of cooling channels arises, in which the cooling channels are in each case arranged in the manner of a sandwich and orientated in a manner inclined relative to the horizontal.